Digital tuning uses a PLL (Phase Locked Loop), basically the oscillator has to be a VCO (Voltage Controlled Oscillator). You divide the oscillator frequency down using a programmable divider, and compare it to a reference frequency - it makes life easier if the reference frequency is the channel spacing, but this isn't essential. The frequency comparator produces an error signal, this is used to change the voltage to the VCO, altering it's frequency. When the VCO reaches the corrent frequency there's no error produced, and the PLL is locked on frequency - if it drifts at all the PLL will correct it.DigiTan said:Yeah, the text says at the bottom that you can adjust the tuning using the 15-120pf capacitor--or by compressing the coil L1 with your hand.
I'm curious to know how digital tuners work. Is it possible to apply a digital tuning device to this design as well?
A quick google found this on-line book, which you may find useful-=GST=- Nemisis (cs/cz) said:i just about understood that :? could you say what to do in a simpler way, or where i can get a digital superhet design like you said and how to install it.